CA1292887C - Method in the bleaching of cellulose pulp - Google Patents
Method in the bleaching of cellulose pulpInfo
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- CA1292887C CA1292887C CA000523659A CA523659A CA1292887C CA 1292887 C CA1292887 C CA 1292887C CA 000523659 A CA000523659 A CA 000523659A CA 523659 A CA523659 A CA 523659A CA 1292887 C CA1292887 C CA 1292887C
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Abstract
Method in the bleaching of cellulose pulp ABSTRACT
When bleaching cellulose pulp with strongly oxidative bleaching agents there is the need for an analysis method which is capable of quickly providing a correct analysis result without complicated manipulation of the bleaching liquor sample. The present invention satisfies this need and relates to a method for measuring the chemical content of bleaching liquor within the cellulose pulp industry, in which a sample of the bleaching liquor is brought together with one or more reagents, of which at least one is chemi-luminescent so as to result in the emission of light, and the intensity of the light is determined as a measurement of the chemical content. The method is characterized in that a constant flow of reagent is advanced continuously through a conduit system and in that a small quantity of sample liquor is introduced sporadically or intermittently into said rea-gent flow so as to produce a chemiluminescent reaction, and in that the reaction, and therewith the emission of light, is caused to continue for a given period of time such that the light intensity falls within the measuring range of a light responsive device, and in that, with repeated measure-ments the light intensity is constantly measured after said time interval, and in that measured values of the light in-tensity are converted to the content of bleaching chemical.
The invention also relates to apparatus for carrying out the aforedescribed method.
When bleaching cellulose pulp with strongly oxidative bleaching agents there is the need for an analysis method which is capable of quickly providing a correct analysis result without complicated manipulation of the bleaching liquor sample. The present invention satisfies this need and relates to a method for measuring the chemical content of bleaching liquor within the cellulose pulp industry, in which a sample of the bleaching liquor is brought together with one or more reagents, of which at least one is chemi-luminescent so as to result in the emission of light, and the intensity of the light is determined as a measurement of the chemical content. The method is characterized in that a constant flow of reagent is advanced continuously through a conduit system and in that a small quantity of sample liquor is introduced sporadically or intermittently into said rea-gent flow so as to produce a chemiluminescent reaction, and in that the reaction, and therewith the emission of light, is caused to continue for a given period of time such that the light intensity falls within the measuring range of a light responsive device, and in that, with repeated measure-ments the light intensity is constantly measured after said time interval, and in that measured values of the light in-tensity are converted to the content of bleaching chemical.
The invention also relates to apparatus for carrying out the aforedescribed method.
Description
lZ9ZE~87 Method ln the bleachlnq of cellulose Pulp Technlcal Fleld The present lnvention relates to a method for measuring the chemical content of llquors used ln the bleaching of cellulose pulp. The method can be applled ln con~unctlon wlth the bleaching of all cellulose pulps, lrrespectlve of thelr llgnin contents, l.e. lncludlng, for example, cheml-cal pulp, chemlmechanical pulp, semlchemlcal pulp and mecha-nical pulp.
Back~round Prlor Art Cellulose pulp is bleached for a number of reasons. One reason ls to decrease the lignln content of the pulp, whereas in the case, for example, of chemlcal pulps the ob-~ectlve is to remove the lignln totally. Another reason for bleachlng pulp is to lncrease its brightness. It ls often endeavoured to both remove llgnin from the pulp and to ln-crease the brightness thereof.
Different bleachlng agents have different effects on cellulose pulp, and can be divided into bleaching agents whlch remove lignln and bleachlng agents whlch preserve the lignin. Examples of lignln removing bleaching agents lnclude chlorlne, chlorine dioxlde, hypochlorite, chlorite, oxygen gas and ozone. Various kinds of peroxide, dithlonlte and boron hydride constitute examples of lignln preservlng bleachlng agents. Some of these bleachlng agents possess both of the aforesaid properties. The pulp ls normally treated wlth alkali between the various bleachlng stages and washed thereafter to remove dissolved materlal.
Back~round Prlor Art Cellulose pulp is bleached for a number of reasons. One reason ls to decrease the lignln content of the pulp, whereas in the case, for example, of chemlcal pulps the ob-~ectlve is to remove the lignln totally. Another reason for bleachlng pulp is to lncrease its brightness. It ls often endeavoured to both remove llgnin from the pulp and to ln-crease the brightness thereof.
Different bleachlng agents have different effects on cellulose pulp, and can be divided into bleaching agents whlch remove lignln and bleachlng agents whlch preserve the lignin. Examples of lignln removing bleaching agents lnclude chlorlne, chlorine dioxlde, hypochlorite, chlorite, oxygen gas and ozone. Various kinds of peroxide, dithlonlte and boron hydride constitute examples of lignln preservlng bleachlng agents. Some of these bleachlng agents possess both of the aforesaid properties. The pulp ls normally treated wlth alkali between the various bleachlng stages and washed thereafter to remove dissolved materlal.
A number of parameters must be taken lnto account when uslng a glven bleachlng agent, ln order to achleve the result deslred. For example, lt ls normally necessary to check or monitor pulp consistency, temperature, tlme and pH, and also preferably to control these parameters. Another lmportant parameter ls the bleachlng agent content, partly of the actual bleachlng llquor as such and partly subsequent to mixlng the bleaching llquor wlth another llquld phase ln the absence or presence of the pulp. There are many theorles as to how a bleachlng stage should be controlled. Dependlng upon the method of control applled, the bleachlng agent content ls determlned lmmedlately after mlxlng the agent wlth the pulp, at some tlme durlng the bleachlng stage, or upon completlon of the bleachlng process. The bleachlng agent ls often charged to the system in excesslve quantl-tles, ln whlch case the amount of bleachlng agent that remalns ls normally of lnterest.
A relatlvely common method of controlling the supply of bleaching agent to the system, and therewith the amount of bleachlng agent contalned by the pulp suspenslon ls one of measuring the redox potentlal of the suspension and of regulating the charge of bleachlng agent golng out from a predetermined set-polnt value of the redox potentlal, so that the set-polnt value ls reached. In the case of bleach-lng chemlcals, thls method can only be used wlthln a very narrow content range. In addltlon thls partlcular method of measurlng the redox potentlal ln the pulp suspenslon is dependent on temperature, to which is added the problem of coatings on the measuring electrodes.
From the chlldhood of bleachlng technology up to the present day, samples of bleachlng agent solutlons have been taken manually (and are stlll taken manually) at relatlvely wlde tlme lntervals, these samples being titrated manually, e.g. iodometrlcally, to arrlve at a given bleaching agent content.
A relatlvely common method of controlling the supply of bleaching agent to the system, and therewith the amount of bleachlng agent contalned by the pulp suspenslon ls one of measuring the redox potentlal of the suspension and of regulating the charge of bleachlng agent golng out from a predetermined set-polnt value of the redox potentlal, so that the set-polnt value ls reached. In the case of bleach-lng chemlcals, thls method can only be used wlthln a very narrow content range. In addltlon thls partlcular method of measurlng the redox potentlal ln the pulp suspenslon is dependent on temperature, to which is added the problem of coatings on the measuring electrodes.
From the chlldhood of bleachlng technology up to the present day, samples of bleachlng agent solutlons have been taken manually (and are stlll taken manually) at relatlvely wlde tlme lntervals, these samples being titrated manually, e.g. iodometrlcally, to arrlve at a given bleaching agent content.
3 lZ9~887 The samples are taken at one or more locatlons wlthln the bleachlng department, e.g. from the actual bleachlng llquor before lt ls mlxed lnto the pulp, or from the sus-pension llquor subsequent to mixlng the bleachlng llquor into the pulp, l.e. durlng an ongolng bleachlng process, or from the suspenslon llquld subsequent to completlon of a bleaching process, l.e. ln order to determlne the resldual content of bleachlng chemlcals of the suspenslon llquor.
Thls partlcular methodology results ln poor coverage of what actually takes place durlng bleachlng of the pulp, partly because the samples are taken at random, and partly because of the relatlvely long perlod of tlme that lapses from the tlme of taklng the sample to the tlme at whlch the operator ln the bleachlng department recelves the lnformatlon con-cernlng the content of the bleachlng agent concerned.
With regard to strongly oxldatlve bleachlng agents, suchas chlorlne and chlorlne dloxlde, lt has been suggested ln Swedlsh Patent Speclflcatlon No. 731412g-3 (399 966) that samples of liquor contalnlng these bleachlng agents shall be reacted wlth a chemlluminescent reactant, leadlng to the emlsslon of light. The total amount of llght emltted ls measured, and the value obtalned provldes data relatlng to the content of the bleachlng agent concerned. The method ln questlon ls lntended prlmarlly for determlnlng both the chlorlne content and the chlorlne dloxlde content of one and the same bleachlng llquor sample, which has prevlously been lmposslble to achleve to any satlsfactory degree of success.
Thls method can be àpplled to partlcular advantage ln bleachlng stages ln whlch a mlxture of chlorlne and chlorlne dloxlde ls used.
Thls partlcular methodology results ln poor coverage of what actually takes place durlng bleachlng of the pulp, partly because the samples are taken at random, and partly because of the relatlvely long perlod of tlme that lapses from the tlme of taklng the sample to the tlme at whlch the operator ln the bleachlng department recelves the lnformatlon con-cernlng the content of the bleachlng agent concerned.
With regard to strongly oxldatlve bleachlng agents, suchas chlorlne and chlorlne dloxlde, lt has been suggested ln Swedlsh Patent Speclflcatlon No. 731412g-3 (399 966) that samples of liquor contalnlng these bleachlng agents shall be reacted wlth a chemlluminescent reactant, leadlng to the emlsslon of light. The total amount of llght emltted ls measured, and the value obtalned provldes data relatlng to the content of the bleachlng agent concerned. The method ln questlon ls lntended prlmarlly for determlnlng both the chlorlne content and the chlorlne dloxlde content of one and the same bleachlng llquor sample, which has prevlously been lmposslble to achleve to any satlsfactory degree of success.
Thls method can be àpplled to partlcular advantage ln bleachlng stages ln whlch a mlxture of chlorlne and chlorlne dloxlde ls used.
4 ~Z9Z8~37 summarY of the Inventlon Technlcal Problem There has been found wlthln the cellulose pulp lndustry, and partlcularly when uslng strongly oxldatlve bleachlng agents, the need for an automated method of analysls whlch s whlle belng rellable and requlrlng but llttle malntenance, spans a wlde range of bleachlng chemlcal concentratlons, and whlch can be applled at relatlvely low costs.
Solutlon The present lnventlon satlsfles thls need and relates to a method for measurlng the chemlcal content of bleachlng llquor wlthln the cellulose pulp lndustry, ln whlch method a bleachlng llquor sample ls admlxed wlth one or more reagents of whlch at least one 16 chemllumlnescent resulting ln llght emlsslon, and the lntenslty of the llght emltted ls deter-mlned as a measure of the chemlcal content, characterlzed bycontlnuously advanclng a flow of reagent through a condult system; lntroduclng a small quantlty of sample llquld spora-dlcally or lntermlttently lnto the flow of reagent so as to produce a chemllumlnescent reactlon; contlnulng the reac-tlon, and therewlth the emlsslon of llght, over a glvenperlod of tlme, so that the llght lntenslty ls such as to fall wlthln the measurlng range of a llght sensltlve or re-sponslve devlce; constantly measurlng the llght lntenslty after sald glven tlme lnterval at repeated measurlng opera-tlons; and convertlng the measured value of llght lntensltyto the content of bleachlng chemlcal.
~ 5 129Z887 The condults used when applylng the method accordlng to the lnventlon are preferably transparent, at least wlthln the reglon thereof ln which the light sensitive measurlng devlce ls located, although lt is fully posslble to use a condult system ln whlch all parts thereof are opaque. In thls latter case, one end of a flbre optlc cable can be con-nected to a non-transparent condult system at a glven location therein, whlle the other end of the cable can be connected to a llght responsive measurlng devlce.
Accordlng to one preferred embodlment of the lnventlon, the reagent ls supplled from a contalner through a condult system whlch can be closed, so that substantlally all unused reagent ls returned to the contalner.
It ls also preferred that the sample llquor contalnlng the bleachlng chemlcal concerned ls dellvered through a con-dult system to a mlxlng locatlon at whlch, vla at least one multl-path valve, elther a small amount of the sample llquor ls lntroduced lnto the flow of reagent or the sample llquor ls conducted beyond the flow of reagent tc an outlet.
Instead of lntroduclng the sample llquor lnto the rea-gent flow ln small quantltles, vla a valve and a condult loop connected thereto, the sample llquor can be introduced lnto the reagent flow by means of so-called hydrodynamlc ln~ectlon, as deflned herelnafter, while uslng a short sec-tlon of the reagent flow located ln the condult system.
That part of the reagent flow whlch comes lnto contact wlth the sample llquor and reacts therewlth to cause llght to be emltted ls caused to leave the condult system, through a sample plpe fltted wlth a valve, subsequent to measurlng the lntenslty of the llght emltted.
In accordance wlth the lnventlon, lt ls also posslble to take separate samples of llquor contalnlng one or more bleachlng chemlcals at selected locations ln the pulp mlll 6 lZ9Z8~7 and to lntroduce sald samples lnto the reagent flow with the ald of a volumetrically graduated devlce. One example of such a devlce is a syrlnge provided wlth a cannula whlch can be lnserted through the wall of the condult carrylng the reagent. The dlstance ln length and/or tlme calculated between the locatlon a~ whlch the sample ls lntroduced and the locatlon at whlch the lntenslty of the llght emltted ls measured must be exactly the same at each tlme of measurlng, even ln the case of the samples ~ust mentioned.
The llght responslve devlce wlth whlch the intenslty of the llght ls measured, may be of any sultable known klnd. In accordance wlth the lnventlon, however, the devlce is pre-ferably ln the form of a dlode capable of convertlng llght energy lnto electrlc voltage resultlng ln a reglsterable slgnal. It has surprlslngly been found that the output slg-nal obtained from the dlode has the form of a curve of sub-stantlally normal dlstrlbutlon, l.e. a so-called Gauss curve. Both the area of the curve and lts peak helght, l.e.
the dlstance from the top of the curve down to lts base, can be related dlrectly to the amount ln whlch a glven bleachlng chemlcal ls present ln the sample. Thls has been establlshed by lntroduclng lnto the aforedescrlbed condult system a sample of llquor whlch contalned a bleachlng chemlcal of known concentratlon and by measurlng the llght lntenslty at a glven polnt of tlme, whlch resulted ln the prlntlng of a curve of the aforesald klnd.
The analysls method accordlng to the lnventlon can be used wlth all bleachlng agents that are capable of reactlng ln a chemllumlnescent fashlon. The lnventlon ls partlcularly useful for analyslng bleachlng llquors that contaln chlo-rlne, chlorlne dloxlde, hypochlorlte, chlorlte, or peroxlde, ln some form or another.
The analysls method accordlng to the lnventlon can be used to advantage both when manlpulatlng actual bleachlng llquors as such, for example ln bleachlng llquor preparatlon processes, and for bleachlng department monltorlng and/or controlllng purposes.
7 12~8~7 The invention also relates to apparatus for measuring the chemical content of bleaching llquor in the cellulose pulp industry, thls apparatus lncludlng means for storlng a chemilumlnescent reagent solutlon, a closed conduit system whlch lncorporates a branch llne capable of being connected to an outlet and through which the reagent solutlon ls ad-vanced by means of a pump means, a further condult system for advanclng a bleaching llquor sample solutlon with the aid of said pump means or some other pump means, and means for lntroduclng a glven quantity of sample solutlon lnto the reagent solution conduit system, by displacing the reagent solution with the sample solution, characterized in that the reagent solutlon condult system has a speclflc length cal-culated from the locatlon at whlch the sample solution is introduced lnto sald system to a location ln a sald system at whlch a llght responslve device measures the lntenslty of the light emltted as a result of a reactlon between the che-mllumlnescent reagent solutlon and the sample solutlon con-talnlng bleachlng agent.
Advantaqes The method accordlng to the lnvention affords a number of advantages. For example, wlth the aid of the lnvention, it is possible to determlne the content of a glven bleachlng chemlcal, e.g. hydrogen peroxlde, ln a bleaGhlng llquor, from small to large chemlcal contents, wlthout needlng to prepare the sample ln any partlcular way, e.g. by hlghly dllutlng the sample. Another advantage ls one of low che-mical consumption, whlch enables the cost of procurlng the chemlcials to be kept at a low level. Even though all chemi-luminescent reagents are highly expensive, calculated inkilograms for example, the fact that the conduit system according to the invention is closed means that only very small volumes of reagent wlll pass to the outlet. These small volumes are also ensured by the fact that in accor-dance wlth the inventlon it is possible to use liquor deli-very pipes or hoses of very small cross-sectional area.
-~ 12~Z887 The actual analysls method as such has also been found to be particularly rellable. It ls especlally surprislng that the reglstered curve form of the slgnal obtalned when repeatedly taklng measurements of one and the same bleachlng llquor sample has a practlcally congruent appearance.
In addltlon the method according to the lnventlon ls hlghly flexlble and has a hlgh avallablllty. The perlodlclty at whlch the varlous analyses are made can be declded upon gulte readlly by the operator responslble. Slnce the reagent solutlon, ln accordance wlth a preferred embodiment of the lnventlon, ls pumped constantly around a condult system ln whlch no reagent solutlon ls lost, lt ls posslble for the temporal dlstance between the sampllng occaslons to be selected ln perlods whlch are ln excess of hours and down to some tenths of a second.
Brlef Descrlptlon of the Drawlnqs Flgure 1 lllustrates an array of apparatus for carrylng out a preferred embodlment of the method accordlng to the lnventlon. Flgure 2 lllustrates an alternatlve method for lntroduclng sample llquor lnto the reagent llquor condult system, and Flgure 3 lllustrates an example of the measurlng slgnal recorded ln curveform when practlslng a preferred embodlment of the lnventlon.
DescrlPtlon of the Best Embodlment lnltlally, preferred embodlments of the lnventlon wlll be descrlbed wlth reference to Flgures 1, 2 and 3, followed by a number of worklng examples.
The manner ln whlch the method accordlng to the lnven-tlon can be applled concretely ls made evident in Flgure 1.
The reference 1 deslgnates a contalner ln whlch the reagent solutlon ls fitored. When necessary, further reagent solutlon ls supplled through the condult 2. The composltlon of the reagent solution may vary, although at least one of the com-ponents must always be a chemlcal whlch ls chemllumlnescent, 9 lZ9Z887 l.e. a ~ubstance whlch reacts wlth certaln other substances whlle emlttlng llght at the same tlme. There are several chemllumlnescent reagents which can be used ln the method accordlng to the lnventlon. One well known substance of thls klnd ls deslgnated luminol. In additlon to lumlnol, the reagent solutlon normally also contalns copper chlorlde, 60dlum bicarbonate and sodium carbonate dlssolved ln water.
The reagent solutlon ls passed, vla the conduit 3 and the pump 4, to two four-path valves whlch form a unit 5. Any known pump whatsoever may be lnstalled at the posltlon 4. A
perstaltlc pump ls preferred however. When thls type of pump ls used, the condult 3 may comprlse a Teflon* hose. It has been found ln practlce that a Teflon*hose havlng a dlameter of 0.7 mm functlons admlrably. Teflon*hoses are transparent.
The method accordlng to the lnventlon ls not llmlted to the use of such hoses or condults however. It ls fully posslble to use hoses or conduits whlch are not transparent. However, ln thls case, ln accordance wlth a preferred embodlment of the lnventlon, that part of the condult or hose sltuated in the reglon where the llght responslve measurlng devlce 7 is located shall be transparent. Thls sectlon of the condult may comprlse a Teflon~ hose or a condult sectlon of some other llght-permeable materlal, such as a glass pipe. In those lnstances when no analysls ls carrled out, the pumpable reagent 601utlon ls pumped stralght through the unlt 5 and through the loop 6, for further transportatlon through ehe measurlng devlce 8 lncorporatlng a light re-sponslve device 7 and back to the contalner 1, vla the condult 10 fitted wlth the valve 9. It ls essentlal that the reagent solutlon ls advanced at a constant rate of flow. It has been found, for example, that a flow rate of 2.5 ml reagent solutlon per mlnute can be used.
The sample llquor, l.e. the llquld whlch contalns the bleaching chemlcal whose concentratlon ls to be determlned by analysls, ls advanced by means of the pump 4 through the condult 11, the distributing device 12 and the condult 13 to * trade mark ~2 ~Z ~
the valve unlt 5. ~hen no analysis is carrled out, the samp-le liquor ls caused to enter the valve unit 5 on one slde thereof, whereupon the llquor passes through the loop or by~pass 14 and out of the unlt 5 on the opposite side there-of~ for continued passage through the condult 13 to an out-let. ~hen the sample llquor ls to be analysed, the two val-ves in the unit 5 are set ln a manner to interrupt the flow of reagent 601ution through the conduit 3 by a volume (or length) whlch corresponds to the volume of llguid (or the length) present 1n the loop 14. Subse~uent to introduclng the sample into the condu1t 3, the ~alves are re-set to the ~tarting po~ition. As a result hereof there is o~talned in the condult 3 to the right of the unlt 5 a sample liquor cylinder of given length which ls embraced by reaction solu-tion on both 6ide~ thereof. As thls takes place, the reac-tlon liquor begin6 to penetrate and mlx with the sample llquld from both 6~de thereof, resulting in a chemilumine-scent reactlon, whlch cau~es light to be emitted. It has been found difflcult wlth the use of known llght lntensity meter~ to mea~ure the intensity of the l~ght in the imme-diate vicinlty of the locatlon at whlch the reagent and the bleachlng chemlcal mlx together and obtain at the same tlme a dlstinct or characteri~tlc signal, i.e. a measurement value whlch correlates to a given concentratlon of the bleaching chemical. Consequently, test6 were carried out in which the aforesald cyllnder of 6ample liquor was permltted to pa66 through a conduit loop 6 of given length to a posl-tion ~ which lncorporated a measurlng apparatus (e.g. in the form of a light impervious box) provided ~ith a llght re-sponsive measuring device 7. The afore6aid length, or dimen-sion, of the loop, or coll, ls directly convertible to a given di6placement in t~me. It h~s ~urprislngly been found t~at with the aid, e.g., of a photodlode placed in the imme-diate vicinlty of the condult wlthin the box B and at a given time di~tance from the moment at which the 6ample liquor was introduced, it is po66ible to mea~ure the inten-sity Df the light emitted ~o as to obtaln a 6ignal ln 1 ~ 1292887 the form of a curve on the prlnter 15 whlch stands ln dlrect relatlonshlp wlth the concentratlon of the bleachlng cheml-cal concerned ln the sample llquor. The photodlode converts llght to electrlc voltage. In order to obtaln a useable curve, the measured slgnal ls preferably ampllfled before belng prlnted by the prlnter 15.
~lth regard to the aforesald dlsplacement ln tlme, l.e. the tlme perlod between lntroduclng the sample lnto the condult carrylng the reagent and measurlng the lntenslty of the light emltted, thls tlme displacement ls dependent on a plurallty of factors, such, as lnter alla, the dlameter of the condult, the rate of flow, the volume of sample llquor.
Convenlently, the chemllumlnescent reactlon ls allowed to contlnued for 2-60 seconds, preferably 15-30 seconds. The most essential factor ln this connectlon, however, ls that all measurements are taken wlth exactly the same tlme exten-slons. The aforementloned preferred tlme lnterval ls prlma-rlly appllcable when analyslng bleachlng llquor that con-talns hydrogen peroxlde. Consequently, ln order to enable each lndlvlual bleachlng agent used lndustrlally to be ana-lysed lt ls necessary to determlne approprlate reactlon tlmes, prlor to measuring the llght lntenslty, wlth the ald of sultable tests. For example, the reaction tlme required for chlorlne-contalnlng bleachlng agents, such as chlorlne, chlorlne dloxlde and hypochlorlte, ls much shorter than that requlred for hydrogen peroxlde.
Any suitable llght responslve measurlng devlce may be used, as an alternatlve to the aforesald photodlode. Exam-ples of such devlces lnclude phototranslstors, photoresls-tors and photomultlpllers.
The sample llquld may be advanced through the system atany deslred rate of flow. The flow rate of the sample liquor ls of secondary lmportance~ slnce lt ls the volume, and then prlmarlly the length of the loop 14, whlch determlnes the amount of sample on whlch the analysls ls carrled out. The 12 i ~Z ~7 loop 14, or shunt, ls completely fllled wlth llquor as the sample llquor ls advanced, lrrespectlve of the speed at whlc~ the sample liquor ls transported. By uslng the same pump 4 as that used to transpor~ the reagent solutlon, and the same type of hose as that used for said reagent solu-tlon, for example, a Teflon hose havlng a dlameter of 0.7 mm, the same flow rate ls also obtalned, for example 2.5 ml of sample llquor per mlnute.
When uslng the aforedescrlbed analysls system for con-trolllng bleachlng processes, the condult 11 ls preferablyconnected to an arrangement of apparatus whlch enables a flow of ~ample llquor to be taken whlch ls substantlally totally free of pulp flbres. Any sultable known klnd of sampllng apparatus can be used. For example, there are found on the market apparatus whlch can be partlally lnserted lnto, for example, a condult through whlch a pulp suspenslon contalnlng a glven bleachlng agent ls transported. That part of the apparatus, or devlce, lnserted lnto the pulp suspen-sion conslsts of a slotted tube, and part of the suspenslon llquor ls caused to pass through the slots and lnto the tube for further transportatlon to, e.g., a buffer vessel, from whlch the flow of sample llquor, or lndlvldual samples of the bleachlng llquor, can be taken for analysls purposes. In order to ensure that the sample llquor ls totally free of flbres and also of other lmpurltles, such as resln partlcles etc., lt may be necessary to pass the sample llquor through a wlre fllter of some 6ultable klnd.
Subsequent to taklng the aforesald measurement, the re-acted chemlcals are permltted to pass through the condult 16 to an outlet. Thls 16 effected by closlng the valve 9 ln the condult 10 and openlng the valve 17 ln the condult 16. The valve 17 need only be held open for a very short perlod of tlme. As a result hereof the reagent solutlon taken from the contalner 1 ls passed back thereto durlng, e.g. at least 95% of the tlme, resultlng ln extremely low consumptlon and therewlth low reagent chemlcal costs.
In order to comprehend the slgnlflcance of the measured slgnal wlth regard to the content of a glven bleachlng chemlcal ln the sample llquor, lt ls necessary to callbrate the system by lntroduclng bleachlng agent solutlons of known content of a glven bleachlng agent. It has been found ad-vantageous to callbrate the system whlle uslng one and the same chemllumlnescent bleachlng agent, but ln dlfferent con-centrations, l.e. a solution contalnlng the bleachlng agentin a relatlvely low concentratlon and a further solutlon contalnlng sald bleachlng agent ln a relatlvely high concen-tratlon. These solutlons are lntroduced lnto the system through the conduit 18 and the condult 19 respectively. By measurlng the peak height on the curve obtalned wlth re-6pectlve solutlons and placlng sald peak helght in relation to the known concentratlon ln, for example, grams of bleach-lng agent per llter of 601ution, lt 16 possible when analys-lng a 6ample contalnlng an unknown quantity of bleachlng agent, 6ub6equent to 6tudylng the recorded curve and its peak helght, to convert the 61gnal in question to informa-tlon concerning the bleachlng agent content of the sample llquor in gram6 per liter.
The 6y6tem 6hould be callbrated at unlform time inter-vals, 61nce certaln dl6crepancle6 can occur in the system.Such dl6crepancle6 can be cau~ed by aglng of the hoses used ln the 6y6tem, whlch ln turn affect6 the flow rate, the flow rate belng an lmportant parameter whlch must be held con-6tant ln order to achleve a 6atlsfactory analysls result.
The pump or pump6 lncorporated ln the 6ystem must al~o be nonltored and checked. If 60 de61red, the analysl6 system lllu6trated ln Flgure 1 can be manlpulated manually, lm-plylng that the operator manually 6tart6 the pump 4, closes the valve 17 and open6 the valve 9 and permits the reagent 601utlon to clrculate around the 6ystem for a short period prior to carrying out an analy6i6. During this period the 14 12~Z887 sample is also pumped ln lts respectlve condults through the system, vla the condult 13 to She aforesald outlet. The valves in the valve unit S are re-set at a selected polnt ln tlme, so as to temporarily lnterrupt transportatlon of the reagent solution and to introduce the content of the loop or ~hunt 14 into the condult 3 so that the chemilumlnescent re-action commences. Subsequent to transportlng the aforesaid determined volume of sample liquor through the loop or coll 6 and past the photodlode 7, during slmultaneous reactlon wlth the reagent and the resultant emlsslon of llght, the valve 17 ls opened and the valve 9 ls closed for a brlef period of time, in order to transport consumed chemicals to the outlet through the condult 16.
It ls assumed that the arrangement of apparatus lllus-trated in Flgure 1 wlll enable the sample llquor to be tran-sported contlnuously to the outlet over longer or shorter perlods of tlme. It 15 qulte posslble, however, ln accor-dance wlth the present lnventlon to supply lndlvidual samp-les of the bleaching liquor, optionally over relatlvely long lntervals of time. When the lnvention ls applied in this manner, it may be sultable to use two pumps at the locatlon 4, a first pump for continuously transportlng a constant flow of reagent solution, as described above, and a second pump, together with an associated condult system, for trans-portlng the optlonally llmlted volume of sample llquor that ls avallable. The amount of sample liquor on whlch the ana-lysis ls carried out i5 also determined in this case by the length of the loop 14 (and a condult area whlch possibly deviates from that of the conduit 3).
In accordance with one preferred embodiment of the in-vention, the analysls system ls controlled by a mlnlcomputer 20, lnstead of being controlled manually. The minlcomputer can be programmed specifically to control, for example, whlch of the liquors carrled ln the conduits 11, 18 15 lZ~ Z ~7 or 19 shall be transported through the system. The mlnl-computer can also be programmed to control the posltlons of the valves ln the valve unlt 5, and it is also posslble to program the computer to read the peak helghts of the llght lntenslty curve prlnted ln the prlnter 15. The computer ls readlly capable of convertlng the measured slgnal to the correspondlng correct concentratlon ln, for example, grams per llter of the bleachlng agent concerned. Thus, the minl-computer can be programmed to ensure that samples are ana-lysed at given time intervals, for example every third or fifth minute, and to ensure that a calibratlon is made at glven tlme lntervals, for example each 60th minute.
Figure 2 lllustrates and alternatlve method of lntro-duclng the sample to the advanclng reagent solutlon when carrylng out the method accordlng to the lnventlon.
The reagent solutlon ls transported through the condult 22 for example wlth the ald of perlstaltic pump 21, to the llght measurlng device 23, for further transportatlon through the condult 24 back to the reagent solutlon contalner (not shown). The sample llquor can be transported, for example by means of a perlstaltlc pump 25, through the condult 26 to a part 27 o the condult 22, whlch ls common to both condult systems, and from there back through the condult 28.
When no analysls ls to be carrled out, the valve 29 ln the sampllng condult 30 ls closed and the valve 31 open, whlch means that the reagent solutlon ls caused, by means of the pump 21, to clrculate ln a constant flow ln the closed system lncorporatlng, lnter alla, the condults 22, 27 and 24. When the sample llquor ls to be analysed, the pump 21 ls stopped and the pump 25 started up. The sample llquor ls transported to the condults 26, 27 and 28 for a perlod of time of such long duratlon as to posltlvely ensure that all 16 lZ9Z~
the reagent solutlon wlthln the conduit sectlon 27 has been replaced wlth sample llquor. A suitable tlme ln thls respect ls from 10 to 20 seconds. The pump 25 ls then stopped and the pump 21 started up.
As thls takes place, the sample ls pressed ln the condul~
sectlon 27 to the rlght of the reagent solutlon whlle slmu-lataneously lntroduclng the chemllumlnescent reactlon caused by penetratlon of reagent solutlon from both sldes of the cyllndrlcal body of sample llquor, the length of thls cyllnder correspondlng to the length of the condult sectlon 27. There ls no rlsk of the sample llquor escaplng vla the condult 28, slnce thls condult ls already filled wlth sta-tlonary llquor. Thus, the sample llquor ls forced to the rlght by means of the pump 21, through the condult 22 and to the llght intenslty measurlng devlce 23. In reallty, that part of the condult 22 located between the condult sectlon 27 and the measurlng devlce 23 ls conslderably longer than lllustrated ln Flgure 2 and preferably lncorporates a loop or coll, slmllar to that referenced 6 ln Flgure 1.
Subsequent to measurlng the lntenslty of the llght emltted, the consumed chemlcals are caused to leave the system through the outlet, vla the sampllng conduit 30 and the valve 29. The valve 31 ls kept clo6ed whlle thls takes place.
The deslred quantlty of 6ample liquor to be analysed ls determlned by the selected length of the condult sectlon 27.
The method of supplylng the sample lllustrated ln Flgure 2 is deslgnated hydrodynamlc ln~ectlon.
Figure 3 lllustrates an example of the slgnal whlch can be detected when carrylng out the analysls method accordlng to the lnventlon. The lllustrated curves were obtalned when analyslng a chemllumlnescent bleachlng agent whlle uslng the analysls system lllustrated ln Flgure 1. The lntenslty of the llght emltted was measured by means of photodlode. As a result of the chemllumlnescent reactlons llght ls emltted wlthln the vlslble wavelength range. Photodiodes responslve to llght wlthln the wavelength of 420-675 nanometers are 17 1292~7 sultable for use when practlslng the lnventlon. ~y posi-tioning the photodiode in the lmmedlate vlcinlty of the con-duit and allowlng the photodiode to convert the transmltted light to a voltage lt ls posslble, wlth the ald of an ampli-fylng unlt, to record the measurement slgnal ln the form ofthe curves lllustrated ln Flgure 3. The tests were carried out on three mutally different bleaching llquors, l.e.
bleaching liquors contalnlng one and the same bleaching agent, but ln three dlfferent concentrations.
Wlth regard to the bleaching agent havlng the lowest concentration, three tests were carried wlth the analysls system at three mlnute lntervals. These tests correspond to the three curves shown on the left of the Figure. It wlll be seen that the three curves are practlcally fully congruent.
Both the surface of the curve and the peak height thereof can be used as a measurement of the amount of bleaching chemical present in the sample. The peak helght has been found the most sultable parameter for use in practice. Dup-llcated measurements have been made on bleachlng llquors contalnlng hlgher quantltles of bleaching chemlcal, and surprlslng conformlty was also obtalned ln thls case ln the appearance of both the measured curves ln respectlve tests.
The curves lllustrated ln Flgure 3 have a markedly narrow conflguratlon, l.e. the curves have a small base ln relatlon to thelr helght. The appearance of the curve ls dependent to a large extent on the speed to whlch the prlnter 15 ls set.
Slnce the helght has been found to be the parame~er of prl-mary interest, a low prlnter speed was selected ln order to economlse on prlntlng paper. It has been found that when the prlnter speed ls lncreased, the curves present a substan-tlally normally dlstrlbuted conflguratlon. The conflguratlon of the curve devlates from a strlctly normal dlstrlbutlon prlmarlly due to a delay of the slgnal wlth respect to the rlght-hand curve half, l.e. the right-hand curve half ls not a complete mlrror image of the left-hand curve half.
18 1;~ 8~7 The fact that when practlsing the method accordlng to the lnventlon such readily readable slgnals are obtalned dS
evidenced by the curves ln Flgure 3 ls surprising. The reason why thls is so ls not known. One posslble explanatlon may be that when the mlxture of the sample llquor and the reagent (i.e. the part of the sample liquor which remains in a non-reacted state subsequent to moving through the long transport path up to the measurlng location) reaches the measuring apparatus 8 llght of a certaln lntenslty ls stlll emltted and that when this light enters the measurlng fleld of the photodiode recording of the signal begins, whlle the slgnal increases the more centrally the llght emltted ls located ln the centre of the measurlng fleld of the photo-diode, and conversely decreases ln pace wlth the llght emls-sion as lt approaches the other end of the measurlng field, and finally terminates completely as it leaves the field.
Thls explanation is purely theoretical and has not been con-flrmed scientifically.
Example 1 The present invention can be used particularly for ana-lysing various types of peroxides, such as hydrogen peroxide for example.
The following tests were carried out in order to ascer-tain the rellabllity of the method according to the inven-tlon. A reagent solutlon having the following composition was prepared.
1 part lumlnol 0.015 M dissolved in 0.1 M NaOH
0.1 part copper chloride 0.02 M
1 part carbonate buffer 33.2 g Na2C03 +
53.2 g NaHC03 per llter 4 parts water 1 9 ~2~Z887 Thls reagent solutlon was used when carrying out analysls wlth the use of the arrangement of apparatus lllustrated ln Figure 1. The analysls system was calibrated partly wlth the ald of a hydrogen peroxlde solution, which contained 4 grams per liter, and partly wlth the ald of a hydrogen peroxlde solutlon whlch contalned 18 grams per llter. Samples of bleachlng llquor were then pumped from a full scale cellu-lose pulp bleachlng department. The bleachlng llquors con-talned varying quantltles of hydrogen peroxlde and were transported through the condult 11, the dlstributlng unit 12, the condult 13 and the loop or shunt 14, up to the unlt 5, where they were lntroduced lnto the condult 3 through whlch the reagent solutlon was transported. 20 mlcrollters of sample llquor were used ln the analysls, thls quantlty correspondlng to the volume of the loop 14. When the sample arrlved at the photodlode 7, the lntenslty of the llght emltted was measured and the recorded ~lgnal converted lnto grams of hydrogen peroxlde per llter, in the afroedescrlbed manner.
The condults 3, 11, 13 and 14 used ln the tests com-prlsed Teflon hose havlng an lnternal dlameter of 0.'7 mm. A
perlstaltlc pump was used ln location 4, whlch gave a flow rate of 2.5 ml/mln, both ln re6pect of the reagent 601utlon and of the sample solutlon. The reactlon tlme was 27 seconds, l.e. the tlme from lntroducing the 6ample solutlon lnto the condult 3 at locatlon 5 ln the form of an elongated llquid cylinder and embraced on both short sides or end-walls by the reagent solution, to the time of measurlng the llght lntensity by means of the photodlode 7.
In addition to analyslng the various bleachlng llquors in accordance wlth the inventlon, the llquors were also sub-~ected to lodometrlc tltration.
The results obtained ln respectlve analyses are set forth ln Table 1 below.
~Z~ 7 Table 1 Sample Iodometrlc tltratlon Analysis accordlng to Number the lnventlon g H202/1 g H202/1 1 15.5 15.5 2 10.6 10.2 3 14.0 14.1 4 12.4 12.5 It wlll be seen that good agreement was obtalned between the measurlng results achleved ln accordance wlth the lnventlon and the results obtalned wlth the conventlonal, manual lodo-metrlc tltratlon processes long used ln practlce.
s It 15 important to note that when practlslng the method accordlng to the lnventlon lt ls possible to obtaln data concernlng the hydrogen peroxide contents of a bleachlng llquor both rapldly and directly, even when the content ls comparatlvely hlgh. Thls has prevlously presented a problem.
Peroxldes, such as hydrogen peroxlde, are a common bleachlng agent used when bleachlny mechanlcal and cheml-mechanlcal pulps ln partlcular. Varlous suggestlons have been put forward as to how such bleachlng processes should be carrled out. One 6uggestlon proposes that a bleaching agent solutlon contalnlng a large quantity of hydrogen per-oxlde ls mlxed rapldly lnto the pulp at a relatlvely low pulp conslstency, whereafter the pulp ls pressed to a rela-tlvely hlgh pulp conslstency.
The llguor pressed from the pulp, whlch llquor stlll ~0 contalns a relatlvely large amount of hydrogen peroxlde, ls recycled and mlxed wlth freshly supplled pulp subsequent to addlng further hydrogen peroxlde, l.e. fresh hydrogen per-oxlde. Thls bleachlng method lnvolves the constant 21 lZ~'Z~7 manlpulation of llquors that contaln large quantltles of hydrogen peroxlde, and slnce thls chemical ls expenslve lt ls hlghly deslrable that the hydrogen peroxlde content of the liquors can be determined correctly and qulckly. The analysis method according to the invention satisfies pre-clsely thls desideratum.
The method accordlng to the invention can be applied equally as well wlth other types of peroxldes, includlng organlc peroxldes. Excellent results are also achleved when the analysis method accordlng to the lnventlon ls applled ln con~unctlon with bleachlng processes whlch use other strong-ly oxldatlve bleachlng agents, such as bleaching agent solu-tions tha~ contaln chlorlne, chlorlne dloxide, hypochlorlte etc.
Solutlon The present lnventlon satlsfles thls need and relates to a method for measurlng the chemlcal content of bleachlng llquor wlthln the cellulose pulp lndustry, ln whlch method a bleachlng llquor sample ls admlxed wlth one or more reagents of whlch at least one 16 chemllumlnescent resulting ln llght emlsslon, and the lntenslty of the llght emltted ls deter-mlned as a measure of the chemlcal content, characterlzed bycontlnuously advanclng a flow of reagent through a condult system; lntroduclng a small quantlty of sample llquld spora-dlcally or lntermlttently lnto the flow of reagent so as to produce a chemllumlnescent reactlon; contlnulng the reac-tlon, and therewlth the emlsslon of llght, over a glvenperlod of tlme, so that the llght lntenslty ls such as to fall wlthln the measurlng range of a llght sensltlve or re-sponslve devlce; constantly measurlng the llght lntenslty after sald glven tlme lnterval at repeated measurlng opera-tlons; and convertlng the measured value of llght lntensltyto the content of bleachlng chemlcal.
~ 5 129Z887 The condults used when applylng the method accordlng to the lnventlon are preferably transparent, at least wlthln the reglon thereof ln which the light sensitive measurlng devlce ls located, although lt is fully posslble to use a condult system ln whlch all parts thereof are opaque. In thls latter case, one end of a flbre optlc cable can be con-nected to a non-transparent condult system at a glven location therein, whlle the other end of the cable can be connected to a llght responsive measurlng devlce.
Accordlng to one preferred embodlment of the lnventlon, the reagent ls supplled from a contalner through a condult system whlch can be closed, so that substantlally all unused reagent ls returned to the contalner.
It ls also preferred that the sample llquor contalnlng the bleachlng chemlcal concerned ls dellvered through a con-dult system to a mlxlng locatlon at whlch, vla at least one multl-path valve, elther a small amount of the sample llquor ls lntroduced lnto the flow of reagent or the sample llquor ls conducted beyond the flow of reagent tc an outlet.
Instead of lntroduclng the sample llquor lnto the rea-gent flow ln small quantltles, vla a valve and a condult loop connected thereto, the sample llquor can be introduced lnto the reagent flow by means of so-called hydrodynamlc ln~ectlon, as deflned herelnafter, while uslng a short sec-tlon of the reagent flow located ln the condult system.
That part of the reagent flow whlch comes lnto contact wlth the sample llquor and reacts therewlth to cause llght to be emltted ls caused to leave the condult system, through a sample plpe fltted wlth a valve, subsequent to measurlng the lntenslty of the llght emltted.
In accordance wlth the lnventlon, lt ls also posslble to take separate samples of llquor contalnlng one or more bleachlng chemlcals at selected locations ln the pulp mlll 6 lZ9Z8~7 and to lntroduce sald samples lnto the reagent flow with the ald of a volumetrically graduated devlce. One example of such a devlce is a syrlnge provided wlth a cannula whlch can be lnserted through the wall of the condult carrylng the reagent. The dlstance ln length and/or tlme calculated between the locatlon a~ whlch the sample ls lntroduced and the locatlon at whlch the lntenslty of the llght emltted ls measured must be exactly the same at each tlme of measurlng, even ln the case of the samples ~ust mentioned.
The llght responslve devlce wlth whlch the intenslty of the llght ls measured, may be of any sultable known klnd. In accordance wlth the lnventlon, however, the devlce is pre-ferably ln the form of a dlode capable of convertlng llght energy lnto electrlc voltage resultlng ln a reglsterable slgnal. It has surprlslngly been found that the output slg-nal obtained from the dlode has the form of a curve of sub-stantlally normal dlstrlbutlon, l.e. a so-called Gauss curve. Both the area of the curve and lts peak helght, l.e.
the dlstance from the top of the curve down to lts base, can be related dlrectly to the amount ln whlch a glven bleachlng chemlcal ls present ln the sample. Thls has been establlshed by lntroduclng lnto the aforedescrlbed condult system a sample of llquor whlch contalned a bleachlng chemlcal of known concentratlon and by measurlng the llght lntenslty at a glven polnt of tlme, whlch resulted ln the prlntlng of a curve of the aforesald klnd.
The analysls method accordlng to the lnventlon can be used wlth all bleachlng agents that are capable of reactlng ln a chemllumlnescent fashlon. The lnventlon ls partlcularly useful for analyslng bleachlng llquors that contaln chlo-rlne, chlorlne dloxlde, hypochlorlte, chlorlte, or peroxlde, ln some form or another.
The analysls method accordlng to the lnventlon can be used to advantage both when manlpulatlng actual bleachlng llquors as such, for example ln bleachlng llquor preparatlon processes, and for bleachlng department monltorlng and/or controlllng purposes.
7 12~8~7 The invention also relates to apparatus for measuring the chemical content of bleaching llquor in the cellulose pulp industry, thls apparatus lncludlng means for storlng a chemilumlnescent reagent solutlon, a closed conduit system whlch lncorporates a branch llne capable of being connected to an outlet and through which the reagent solutlon ls ad-vanced by means of a pump means, a further condult system for advanclng a bleaching llquor sample solutlon with the aid of said pump means or some other pump means, and means for lntroduclng a glven quantity of sample solutlon lnto the reagent solution conduit system, by displacing the reagent solution with the sample solution, characterized in that the reagent solutlon condult system has a speclflc length cal-culated from the locatlon at whlch the sample solution is introduced lnto sald system to a location ln a sald system at whlch a llght responslve device measures the lntenslty of the light emltted as a result of a reactlon between the che-mllumlnescent reagent solutlon and the sample solutlon con-talnlng bleachlng agent.
Advantaqes The method accordlng to the lnvention affords a number of advantages. For example, wlth the aid of the lnvention, it is possible to determlne the content of a glven bleachlng chemlcal, e.g. hydrogen peroxlde, ln a bleaGhlng llquor, from small to large chemlcal contents, wlthout needlng to prepare the sample ln any partlcular way, e.g. by hlghly dllutlng the sample. Another advantage ls one of low che-mical consumption, whlch enables the cost of procurlng the chemlcials to be kept at a low level. Even though all chemi-luminescent reagents are highly expensive, calculated inkilograms for example, the fact that the conduit system according to the invention is closed means that only very small volumes of reagent wlll pass to the outlet. These small volumes are also ensured by the fact that in accor-dance wlth the inventlon it is possible to use liquor deli-very pipes or hoses of very small cross-sectional area.
-~ 12~Z887 The actual analysls method as such has also been found to be particularly rellable. It ls especlally surprislng that the reglstered curve form of the slgnal obtalned when repeatedly taklng measurements of one and the same bleachlng llquor sample has a practlcally congruent appearance.
In addltlon the method according to the lnventlon ls hlghly flexlble and has a hlgh avallablllty. The perlodlclty at whlch the varlous analyses are made can be declded upon gulte readlly by the operator responslble. Slnce the reagent solutlon, ln accordance wlth a preferred embodiment of the lnventlon, ls pumped constantly around a condult system ln whlch no reagent solutlon ls lost, lt ls posslble for the temporal dlstance between the sampllng occaslons to be selected ln perlods whlch are ln excess of hours and down to some tenths of a second.
Brlef Descrlptlon of the Drawlnqs Flgure 1 lllustrates an array of apparatus for carrylng out a preferred embodlment of the method accordlng to the lnventlon. Flgure 2 lllustrates an alternatlve method for lntroduclng sample llquor lnto the reagent llquor condult system, and Flgure 3 lllustrates an example of the measurlng slgnal recorded ln curveform when practlslng a preferred embodlment of the lnventlon.
DescrlPtlon of the Best Embodlment lnltlally, preferred embodlments of the lnventlon wlll be descrlbed wlth reference to Flgures 1, 2 and 3, followed by a number of worklng examples.
The manner ln whlch the method accordlng to the lnven-tlon can be applled concretely ls made evident in Flgure 1.
The reference 1 deslgnates a contalner ln whlch the reagent solutlon ls fitored. When necessary, further reagent solutlon ls supplled through the condult 2. The composltlon of the reagent solution may vary, although at least one of the com-ponents must always be a chemlcal whlch ls chemllumlnescent, 9 lZ9Z887 l.e. a ~ubstance whlch reacts wlth certaln other substances whlle emlttlng llght at the same tlme. There are several chemllumlnescent reagents which can be used ln the method accordlng to the lnventlon. One well known substance of thls klnd ls deslgnated luminol. In additlon to lumlnol, the reagent solutlon normally also contalns copper chlorlde, 60dlum bicarbonate and sodium carbonate dlssolved ln water.
The reagent solutlon ls passed, vla the conduit 3 and the pump 4, to two four-path valves whlch form a unit 5. Any known pump whatsoever may be lnstalled at the posltlon 4. A
perstaltlc pump ls preferred however. When thls type of pump ls used, the condult 3 may comprlse a Teflon* hose. It has been found ln practlce that a Teflon*hose havlng a dlameter of 0.7 mm functlons admlrably. Teflon*hoses are transparent.
The method accordlng to the lnventlon ls not llmlted to the use of such hoses or condults however. It ls fully posslble to use hoses or conduits whlch are not transparent. However, ln thls case, ln accordance wlth a preferred embodlment of the lnventlon, that part of the condult or hose sltuated in the reglon where the llght responslve measurlng devlce 7 is located shall be transparent. Thls sectlon of the condult may comprlse a Teflon~ hose or a condult sectlon of some other llght-permeable materlal, such as a glass pipe. In those lnstances when no analysls ls carrled out, the pumpable reagent 601utlon ls pumped stralght through the unlt 5 and through the loop 6, for further transportatlon through ehe measurlng devlce 8 lncorporatlng a light re-sponslve device 7 and back to the contalner 1, vla the condult 10 fitted wlth the valve 9. It ls essentlal that the reagent solutlon ls advanced at a constant rate of flow. It has been found, for example, that a flow rate of 2.5 ml reagent solutlon per mlnute can be used.
The sample llquor, l.e. the llquld whlch contalns the bleaching chemlcal whose concentratlon ls to be determlned by analysls, ls advanced by means of the pump 4 through the condult 11, the distributing device 12 and the condult 13 to * trade mark ~2 ~Z ~
the valve unlt 5. ~hen no analysis is carrled out, the samp-le liquor ls caused to enter the valve unit 5 on one slde thereof, whereupon the llquor passes through the loop or by~pass 14 and out of the unlt 5 on the opposite side there-of~ for continued passage through the condult 13 to an out-let. ~hen the sample llquor ls to be analysed, the two val-ves in the unit 5 are set ln a manner to interrupt the flow of reagent 601ution through the conduit 3 by a volume (or length) whlch corresponds to the volume of llguid (or the length) present 1n the loop 14. Subse~uent to introduclng the sample into the condu1t 3, the ~alves are re-set to the ~tarting po~ition. As a result hereof there is o~talned in the condult 3 to the right of the unlt 5 a sample liquor cylinder of given length which ls embraced by reaction solu-tion on both 6ide~ thereof. As thls takes place, the reac-tlon liquor begin6 to penetrate and mlx with the sample llquld from both 6~de thereof, resulting in a chemilumine-scent reactlon, whlch cau~es light to be emitted. It has been found difflcult wlth the use of known llght lntensity meter~ to mea~ure the intensity of the l~ght in the imme-diate vicinlty of the locatlon at whlch the reagent and the bleachlng chemlcal mlx together and obtain at the same tlme a dlstinct or characteri~tlc signal, i.e. a measurement value whlch correlates to a given concentratlon of the bleaching chemical. Consequently, test6 were carried out in which the aforesald cyllnder of 6ample liquor was permltted to pa66 through a conduit loop 6 of given length to a posl-tion ~ which lncorporated a measurlng apparatus (e.g. in the form of a light impervious box) provided ~ith a llght re-sponsive measuring device 7. The afore6aid length, or dimen-sion, of the loop, or coll, ls directly convertible to a given di6placement in t~me. It h~s ~urprislngly been found t~at with the aid, e.g., of a photodlode placed in the imme-diate vicinlty of the condult wlthin the box B and at a given time di~tance from the moment at which the 6ample liquor was introduced, it is po66ible to mea~ure the inten-sity Df the light emitted ~o as to obtaln a 6ignal ln 1 ~ 1292887 the form of a curve on the prlnter 15 whlch stands ln dlrect relatlonshlp wlth the concentratlon of the bleachlng cheml-cal concerned ln the sample llquor. The photodlode converts llght to electrlc voltage. In order to obtaln a useable curve, the measured slgnal ls preferably ampllfled before belng prlnted by the prlnter 15.
~lth regard to the aforesald dlsplacement ln tlme, l.e. the tlme perlod between lntroduclng the sample lnto the condult carrylng the reagent and measurlng the lntenslty of the light emltted, thls tlme displacement ls dependent on a plurallty of factors, such, as lnter alla, the dlameter of the condult, the rate of flow, the volume of sample llquor.
Convenlently, the chemllumlnescent reactlon ls allowed to contlnued for 2-60 seconds, preferably 15-30 seconds. The most essential factor ln this connectlon, however, ls that all measurements are taken wlth exactly the same tlme exten-slons. The aforementloned preferred tlme lnterval ls prlma-rlly appllcable when analyslng bleachlng llquor that con-talns hydrogen peroxlde. Consequently, ln order to enable each lndlvlual bleachlng agent used lndustrlally to be ana-lysed lt ls necessary to determlne approprlate reactlon tlmes, prlor to measuring the llght lntenslty, wlth the ald of sultable tests. For example, the reaction tlme required for chlorlne-contalnlng bleachlng agents, such as chlorlne, chlorlne dloxlde and hypochlorlte, ls much shorter than that requlred for hydrogen peroxlde.
Any suitable llght responslve measurlng devlce may be used, as an alternatlve to the aforesald photodlode. Exam-ples of such devlces lnclude phototranslstors, photoresls-tors and photomultlpllers.
The sample llquld may be advanced through the system atany deslred rate of flow. The flow rate of the sample liquor ls of secondary lmportance~ slnce lt ls the volume, and then prlmarlly the length of the loop 14, whlch determlnes the amount of sample on whlch the analysls ls carrled out. The 12 i ~Z ~7 loop 14, or shunt, ls completely fllled wlth llquor as the sample llquor ls advanced, lrrespectlve of the speed at whlc~ the sample liquor ls transported. By uslng the same pump 4 as that used to transpor~ the reagent solutlon, and the same type of hose as that used for said reagent solu-tlon, for example, a Teflon hose havlng a dlameter of 0.7 mm, the same flow rate ls also obtalned, for example 2.5 ml of sample llquor per mlnute.
When uslng the aforedescrlbed analysls system for con-trolllng bleachlng processes, the condult 11 ls preferablyconnected to an arrangement of apparatus whlch enables a flow of ~ample llquor to be taken whlch ls substantlally totally free of pulp flbres. Any sultable known klnd of sampllng apparatus can be used. For example, there are found on the market apparatus whlch can be partlally lnserted lnto, for example, a condult through whlch a pulp suspenslon contalnlng a glven bleachlng agent ls transported. That part of the apparatus, or devlce, lnserted lnto the pulp suspen-sion conslsts of a slotted tube, and part of the suspenslon llquor ls caused to pass through the slots and lnto the tube for further transportatlon to, e.g., a buffer vessel, from whlch the flow of sample llquor, or lndlvldual samples of the bleachlng llquor, can be taken for analysls purposes. In order to ensure that the sample llquor ls totally free of flbres and also of other lmpurltles, such as resln partlcles etc., lt may be necessary to pass the sample llquor through a wlre fllter of some 6ultable klnd.
Subsequent to taklng the aforesald measurement, the re-acted chemlcals are permltted to pass through the condult 16 to an outlet. Thls 16 effected by closlng the valve 9 ln the condult 10 and openlng the valve 17 ln the condult 16. The valve 17 need only be held open for a very short perlod of tlme. As a result hereof the reagent solutlon taken from the contalner 1 ls passed back thereto durlng, e.g. at least 95% of the tlme, resultlng ln extremely low consumptlon and therewlth low reagent chemlcal costs.
In order to comprehend the slgnlflcance of the measured slgnal wlth regard to the content of a glven bleachlng chemlcal ln the sample llquor, lt ls necessary to callbrate the system by lntroduclng bleachlng agent solutlons of known content of a glven bleachlng agent. It has been found ad-vantageous to callbrate the system whlle uslng one and the same chemllumlnescent bleachlng agent, but ln dlfferent con-centrations, l.e. a solution contalnlng the bleachlng agentin a relatlvely low concentratlon and a further solutlon contalnlng sald bleachlng agent ln a relatlvely high concen-tratlon. These solutlons are lntroduced lnto the system through the conduit 18 and the condult 19 respectively. By measurlng the peak height on the curve obtalned wlth re-6pectlve solutlons and placlng sald peak helght in relation to the known concentratlon ln, for example, grams of bleach-lng agent per llter of 601ution, lt 16 possible when analys-lng a 6ample contalnlng an unknown quantity of bleachlng agent, 6ub6equent to 6tudylng the recorded curve and its peak helght, to convert the 61gnal in question to informa-tlon concerning the bleachlng agent content of the sample llquor in gram6 per liter.
The 6y6tem 6hould be callbrated at unlform time inter-vals, 61nce certaln dl6crepancle6 can occur in the system.Such dl6crepancle6 can be cau~ed by aglng of the hoses used ln the 6y6tem, whlch ln turn affect6 the flow rate, the flow rate belng an lmportant parameter whlch must be held con-6tant ln order to achleve a 6atlsfactory analysls result.
The pump or pump6 lncorporated ln the 6ystem must al~o be nonltored and checked. If 60 de61red, the analysl6 system lllu6trated ln Flgure 1 can be manlpulated manually, lm-plylng that the operator manually 6tart6 the pump 4, closes the valve 17 and open6 the valve 9 and permits the reagent 601utlon to clrculate around the 6ystem for a short period prior to carrying out an analy6i6. During this period the 14 12~Z887 sample is also pumped ln lts respectlve condults through the system, vla the condult 13 to She aforesald outlet. The valves in the valve unit S are re-set at a selected polnt ln tlme, so as to temporarily lnterrupt transportatlon of the reagent solution and to introduce the content of the loop or ~hunt 14 into the condult 3 so that the chemilumlnescent re-action commences. Subsequent to transportlng the aforesaid determined volume of sample liquor through the loop or coll 6 and past the photodlode 7, during slmultaneous reactlon wlth the reagent and the resultant emlsslon of llght, the valve 17 ls opened and the valve 9 ls closed for a brlef period of time, in order to transport consumed chemicals to the outlet through the condult 16.
It ls assumed that the arrangement of apparatus lllus-trated in Flgure 1 wlll enable the sample llquor to be tran-sported contlnuously to the outlet over longer or shorter perlods of tlme. It 15 qulte posslble, however, ln accor-dance wlth the present lnventlon to supply lndlvidual samp-les of the bleaching liquor, optionally over relatlvely long lntervals of time. When the lnvention ls applied in this manner, it may be sultable to use two pumps at the locatlon 4, a first pump for continuously transportlng a constant flow of reagent solution, as described above, and a second pump, together with an associated condult system, for trans-portlng the optlonally llmlted volume of sample llquor that ls avallable. The amount of sample liquor on whlch the ana-lysis ls carried out i5 also determined in this case by the length of the loop 14 (and a condult area whlch possibly deviates from that of the conduit 3).
In accordance with one preferred embodiment of the in-vention, the analysls system ls controlled by a mlnlcomputer 20, lnstead of being controlled manually. The minlcomputer can be programmed specifically to control, for example, whlch of the liquors carrled ln the conduits 11, 18 15 lZ~ Z ~7 or 19 shall be transported through the system. The mlnl-computer can also be programmed to control the posltlons of the valves ln the valve unlt 5, and it is also posslble to program the computer to read the peak helghts of the llght lntenslty curve prlnted ln the prlnter 15. The computer ls readlly capable of convertlng the measured slgnal to the correspondlng correct concentratlon ln, for example, grams per llter of the bleachlng agent concerned. Thus, the minl-computer can be programmed to ensure that samples are ana-lysed at given time intervals, for example every third or fifth minute, and to ensure that a calibratlon is made at glven tlme lntervals, for example each 60th minute.
Figure 2 lllustrates and alternatlve method of lntro-duclng the sample to the advanclng reagent solutlon when carrylng out the method accordlng to the lnventlon.
The reagent solutlon ls transported through the condult 22 for example wlth the ald of perlstaltic pump 21, to the llght measurlng device 23, for further transportatlon through the condult 24 back to the reagent solutlon contalner (not shown). The sample llquor can be transported, for example by means of a perlstaltlc pump 25, through the condult 26 to a part 27 o the condult 22, whlch ls common to both condult systems, and from there back through the condult 28.
When no analysls ls to be carrled out, the valve 29 ln the sampllng condult 30 ls closed and the valve 31 open, whlch means that the reagent solutlon ls caused, by means of the pump 21, to clrculate ln a constant flow ln the closed system lncorporatlng, lnter alla, the condults 22, 27 and 24. When the sample llquor ls to be analysed, the pump 21 ls stopped and the pump 25 started up. The sample llquor ls transported to the condults 26, 27 and 28 for a perlod of time of such long duratlon as to posltlvely ensure that all 16 lZ9Z~
the reagent solutlon wlthln the conduit sectlon 27 has been replaced wlth sample llquor. A suitable tlme ln thls respect ls from 10 to 20 seconds. The pump 25 ls then stopped and the pump 21 started up.
As thls takes place, the sample ls pressed ln the condul~
sectlon 27 to the rlght of the reagent solutlon whlle slmu-lataneously lntroduclng the chemllumlnescent reactlon caused by penetratlon of reagent solutlon from both sldes of the cyllndrlcal body of sample llquor, the length of thls cyllnder correspondlng to the length of the condult sectlon 27. There ls no rlsk of the sample llquor escaplng vla the condult 28, slnce thls condult ls already filled wlth sta-tlonary llquor. Thus, the sample llquor ls forced to the rlght by means of the pump 21, through the condult 22 and to the llght intenslty measurlng devlce 23. In reallty, that part of the condult 22 located between the condult sectlon 27 and the measurlng devlce 23 ls conslderably longer than lllustrated ln Flgure 2 and preferably lncorporates a loop or coll, slmllar to that referenced 6 ln Flgure 1.
Subsequent to measurlng the lntenslty of the llght emltted, the consumed chemlcals are caused to leave the system through the outlet, vla the sampllng conduit 30 and the valve 29. The valve 31 ls kept clo6ed whlle thls takes place.
The deslred quantlty of 6ample liquor to be analysed ls determlned by the selected length of the condult sectlon 27.
The method of supplylng the sample lllustrated ln Flgure 2 is deslgnated hydrodynamlc ln~ectlon.
Figure 3 lllustrates an example of the slgnal whlch can be detected when carrylng out the analysls method accordlng to the lnventlon. The lllustrated curves were obtalned when analyslng a chemllumlnescent bleachlng agent whlle uslng the analysls system lllustrated ln Flgure 1. The lntenslty of the llght emltted was measured by means of photodlode. As a result of the chemllumlnescent reactlons llght ls emltted wlthln the vlslble wavelength range. Photodiodes responslve to llght wlthln the wavelength of 420-675 nanometers are 17 1292~7 sultable for use when practlslng the lnventlon. ~y posi-tioning the photodiode in the lmmedlate vlcinlty of the con-duit and allowlng the photodiode to convert the transmltted light to a voltage lt ls posslble, wlth the ald of an ampli-fylng unlt, to record the measurement slgnal ln the form ofthe curves lllustrated ln Flgure 3. The tests were carried out on three mutally different bleaching llquors, l.e.
bleaching liquors contalnlng one and the same bleaching agent, but ln three dlfferent concentrations.
Wlth regard to the bleaching agent havlng the lowest concentration, three tests were carried wlth the analysls system at three mlnute lntervals. These tests correspond to the three curves shown on the left of the Figure. It wlll be seen that the three curves are practlcally fully congruent.
Both the surface of the curve and the peak height thereof can be used as a measurement of the amount of bleaching chemical present in the sample. The peak helght has been found the most sultable parameter for use in practice. Dup-llcated measurements have been made on bleachlng llquors contalnlng hlgher quantltles of bleaching chemlcal, and surprlslng conformlty was also obtalned ln thls case ln the appearance of both the measured curves ln respectlve tests.
The curves lllustrated ln Flgure 3 have a markedly narrow conflguratlon, l.e. the curves have a small base ln relatlon to thelr helght. The appearance of the curve ls dependent to a large extent on the speed to whlch the prlnter 15 ls set.
Slnce the helght has been found to be the parame~er of prl-mary interest, a low prlnter speed was selected ln order to economlse on prlntlng paper. It has been found that when the prlnter speed ls lncreased, the curves present a substan-tlally normally dlstrlbuted conflguratlon. The conflguratlon of the curve devlates from a strlctly normal dlstrlbutlon prlmarlly due to a delay of the slgnal wlth respect to the rlght-hand curve half, l.e. the right-hand curve half ls not a complete mlrror image of the left-hand curve half.
18 1;~ 8~7 The fact that when practlsing the method accordlng to the lnventlon such readily readable slgnals are obtalned dS
evidenced by the curves ln Flgure 3 ls surprising. The reason why thls is so ls not known. One posslble explanatlon may be that when the mlxture of the sample llquor and the reagent (i.e. the part of the sample liquor which remains in a non-reacted state subsequent to moving through the long transport path up to the measurlng location) reaches the measuring apparatus 8 llght of a certaln lntenslty ls stlll emltted and that when this light enters the measurlng fleld of the photodiode recording of the signal begins, whlle the slgnal increases the more centrally the llght emltted ls located ln the centre of the measurlng fleld of the photo-diode, and conversely decreases ln pace wlth the llght emls-sion as lt approaches the other end of the measurlng field, and finally terminates completely as it leaves the field.
Thls explanation is purely theoretical and has not been con-flrmed scientifically.
Example 1 The present invention can be used particularly for ana-lysing various types of peroxides, such as hydrogen peroxide for example.
The following tests were carried out in order to ascer-tain the rellabllity of the method according to the inven-tlon. A reagent solutlon having the following composition was prepared.
1 part lumlnol 0.015 M dissolved in 0.1 M NaOH
0.1 part copper chloride 0.02 M
1 part carbonate buffer 33.2 g Na2C03 +
53.2 g NaHC03 per llter 4 parts water 1 9 ~2~Z887 Thls reagent solutlon was used when carrying out analysls wlth the use of the arrangement of apparatus lllustrated ln Figure 1. The analysls system was calibrated partly wlth the ald of a hydrogen peroxlde solution, which contained 4 grams per liter, and partly wlth the ald of a hydrogen peroxlde solutlon whlch contalned 18 grams per llter. Samples of bleachlng llquor were then pumped from a full scale cellu-lose pulp bleachlng department. The bleachlng llquors con-talned varying quantltles of hydrogen peroxlde and were transported through the condult 11, the dlstributlng unit 12, the condult 13 and the loop or shunt 14, up to the unlt 5, where they were lntroduced lnto the condult 3 through whlch the reagent solutlon was transported. 20 mlcrollters of sample llquor were used ln the analysls, thls quantlty correspondlng to the volume of the loop 14. When the sample arrlved at the photodlode 7, the lntenslty of the llght emltted was measured and the recorded ~lgnal converted lnto grams of hydrogen peroxlde per llter, in the afroedescrlbed manner.
The condults 3, 11, 13 and 14 used ln the tests com-prlsed Teflon hose havlng an lnternal dlameter of 0.'7 mm. A
perlstaltlc pump was used ln location 4, whlch gave a flow rate of 2.5 ml/mln, both ln re6pect of the reagent 601utlon and of the sample solutlon. The reactlon tlme was 27 seconds, l.e. the tlme from lntroducing the 6ample solutlon lnto the condult 3 at locatlon 5 ln the form of an elongated llquid cylinder and embraced on both short sides or end-walls by the reagent solution, to the time of measurlng the llght lntensity by means of the photodlode 7.
In addition to analyslng the various bleachlng llquors in accordance wlth the inventlon, the llquors were also sub-~ected to lodometrlc tltration.
The results obtained ln respectlve analyses are set forth ln Table 1 below.
~Z~ 7 Table 1 Sample Iodometrlc tltratlon Analysis accordlng to Number the lnventlon g H202/1 g H202/1 1 15.5 15.5 2 10.6 10.2 3 14.0 14.1 4 12.4 12.5 It wlll be seen that good agreement was obtalned between the measurlng results achleved ln accordance wlth the lnventlon and the results obtalned wlth the conventlonal, manual lodo-metrlc tltratlon processes long used ln practlce.
s It 15 important to note that when practlslng the method accordlng to the lnventlon lt ls possible to obtaln data concernlng the hydrogen peroxide contents of a bleachlng llquor both rapldly and directly, even when the content ls comparatlvely hlgh. Thls has prevlously presented a problem.
Peroxldes, such as hydrogen peroxlde, are a common bleachlng agent used when bleachlny mechanlcal and cheml-mechanlcal pulps ln partlcular. Varlous suggestlons have been put forward as to how such bleachlng processes should be carrled out. One 6uggestlon proposes that a bleaching agent solutlon contalnlng a large quantity of hydrogen per-oxlde ls mlxed rapldly lnto the pulp at a relatlvely low pulp conslstency, whereafter the pulp ls pressed to a rela-tlvely hlgh pulp conslstency.
The llguor pressed from the pulp, whlch llquor stlll ~0 contalns a relatlvely large amount of hydrogen peroxlde, ls recycled and mlxed wlth freshly supplled pulp subsequent to addlng further hydrogen peroxlde, l.e. fresh hydrogen per-oxlde. Thls bleachlng method lnvolves the constant 21 lZ~'Z~7 manlpulation of llquors that contaln large quantltles of hydrogen peroxlde, and slnce thls chemical ls expenslve lt ls hlghly deslrable that the hydrogen peroxlde content of the liquors can be determined correctly and qulckly. The analysis method according to the invention satisfies pre-clsely thls desideratum.
The method accordlng to the invention can be applied equally as well wlth other types of peroxldes, includlng organlc peroxldes. Excellent results are also achleved when the analysis method accordlng to the lnventlon ls applled ln con~unctlon with bleachlng processes whlch use other strong-ly oxldatlve bleachlng agents, such as bleaching agent solu-tions tha~ contaln chlorlne, chlorlne dloxide, hypochlorlte etc.
Claims (17)
1. A method for measuring the chemical content of bleaching liquor within the cellulose pulp industry, in which a sample of the bleaching liquor is brought together with one or more reagents, of which at least one is chemiluminescent so as to result in the emission of light, the intensity of which is determined as a measurement of said chemical content, c h a-r a c t e r i z e d b y continuously advancing a con-stant flow of reagent through a conduit system and intro-ducing a small quantity of sample liquor sporadically or intermittently into the flow of reagent, so as to produce a chemiluminescent reaction; causing the reaction, and there-with the emission of light, to continue over a given period of time so that the light intensity is such as to fall within the measuring range of a light responsive device;
with repeated measurements, constantly measuring the light intensity after said time period; and by converting the light intensity to the bleaching chemical content.
with repeated measurements, constantly measuring the light intensity after said time period; and by converting the light intensity to the bleaching chemical content.
2. A method according to Claim 1, c h a r a c t e r i -z e d in that the conduits forming said conduit system are transparent, at least at that part of the system at which the light responsive measuring device is located.
3. A method according to Claim 1, c h a r a c t e r i -z e d in that the reagent is advanced from a container through a conduit system which can be closed so that sub-stantially all unused reagent is returned to the container.
4. A method according to Claim 1, 2 or 3, characterized in that the sample liquor is advanced in a conduit system to a mixing location at which, via at least one multipath valve, either a small quantity of the sample liquor is introduced into the flow of reagent or said sample liquor is conducted past the flow of reagent to an outlet.
5. A method according to Claim 1, 2 or 3, characterized in that the sample liquor is advanced to a mixing location at which a small amount of the sample liquor is hydrodynamically injected into the flow of reagent.
6. A method according to Claim 1, 2 or 3, characterized in that, that part of the reagent flow combined with the sample liquor and caused to react therewith is caused to leave the conduit system, via a sample conduit provided with valve means, subsequent to measuring the intensity of the light emitted.
7. A method according to Claim 1, 2 or 3, characterized in that the amount of sample liquor introduced is controlled by utilizing a given length of the reagent solution conduit system where the reagent solution is displaced by advancing the sample solution.
8. A method according to Claim 1, 2 or 3, characterized in that an individual sample of the bleaching liquor is introduced into the flow of reagent.
9. A method according to Claim 1, characterized in that the intensity of said light is measured by means of a diode capable of converting light energy to an electric voltage resulting in a registered signal.
10. A method according to Claim 9, characterized in that the signal is registered in the form of a curve of substantially normal distribution; and in that the distance from the peak of the curve to the base thereof is measured and used as a direct measurement of the chemical content of the sample subsequent to comparison with the result achieved with liquors having a known chemical content.
11. Apparatus for measuring the chemical content of bleaching liquor within the cellulose pulp industry, comprising means for storing a chemiluminescent reagent solution, and a closed conduit system provided with a closeable sample conduit passing to an outlet, the reagent solution being transported through the conduit system by means of a first pump arrangement, and further comprising a further conduit system for transporting a sample solution of said bleaching liquor by means of a second pump arrangement, and means for introducing a given quantity of sample solution into the reagent solution conduit system, by displacing the reagent solution with the sample solution;
said reagent solution conduit system having a specific length calculated from the location at which the sample solution was introduced to a location in the conduit system at which a light responsive measuring device measures the intensity of the light emitted as a result of a reaction between the chemiluminescent reagent solution and the sample solution containing the bleaching agent.
said reagent solution conduit system having a specific length calculated from the location at which the sample solution was introduced to a location in the conduit system at which a light responsive measuring device measures the intensity of the light emitted as a result of a reaction between the chemiluminescent reagent solution and the sample solution containing the bleaching agent.
12. Apparatus according to Claim 11, wherein at least that part of the reagent solution conduit system in which the light responsive measuring device is located is made of a transparent material.
13. Apparatus according to Claim 11 or 12, wherein the means for introducing a given quantity of sample solution into the reagent solution conduit system comprises two pneumatically controlled and mutually co-acting four-path valves with a connected, short conducting loop or shunt of specific length.
14. Apparatus according to Claim 11 or 12, wherein the means for introducing a given quantity of sample solution into the reagent solution conduit system comprises two conduits which are connected directly to the conduit system at a determined, short distance form each other, and a pump means connected to the conduits.
15. Apparatus according to Claim 11 or 12, wherein the light responsive measuring device is a photodiode which converts the light emitted to a signal in the form of a voltage; and in that the photodiode is incorporated in a light impervious arrangement which also includes means for amplifying the signal obtained from the photodiode, so as to enable the signal to be recorded in a recording means.
16. Apparatus according to Claim 11 or 12, wherein a minicomputer connected to the system controls the transportation of both the reagent solution and the sample solution, and by changing the valve settings ensures that sample liquor is analysed at desired time intervals and that consumed chemicals are caused to leave the system to said outlet, and in that the minicomputer reads the measuring result for conversion thereof to a given content of analysed bleaching agent.
17. Apparatus according to claim 11, wherein said first and second pump arrangements are one in the same.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000523659A CA1292887C (en) | 1986-11-24 | 1986-11-24 | Method in the bleaching of cellulose pulp |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000523659A CA1292887C (en) | 1986-11-24 | 1986-11-24 | Method in the bleaching of cellulose pulp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292887C true CA1292887C (en) | 1991-12-10 |
Family
ID=4134416
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000523659A Expired - Fee Related CA1292887C (en) | 1986-11-24 | 1986-11-24 | Method in the bleaching of cellulose pulp |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1292887C (en) |
-
1986
- 1986-11-24 CA CA000523659A patent/CA1292887C/en not_active Expired - Fee Related
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| Date | Code | Title | Description |
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| MKLA | Lapsed |